Proc. 15th INA Conf., Bohol, Philippines
J. Nannoplankton Res. 36 (2), 2016, pp.121–132 © 2016 International Nannoplankton Association
ISSN 1210-8049 Printed by The Sheridan Press, USA

121

A Cenozoic calcareous nannofossil biozonation from low
and middle latitudes: A synthesis
Isabella Raffi*
Dipartimento di Ingegneria e Geologia, Università “G. d’Annunzio” di Chieti-Pescara, I-66013 Chieti Scalo, Italy; *isabella.raffi@unich.it

Claudia Agnini
Dipartimento di Geoscienze, Università di Padova, I-35131 Padova, Italy

Jan Backman
Department of Geological Sciences, Stockholm University, SE-106 91 Stockholm, Sweden

Rita Catanzariti
Istituto di Geoscienze e Georisorse, CNR-Pisa, I-56124 Pisa, Italy

Heiko Pälike
Center for Marine Environmental Sciences (MARUM), University of Bremen, 28359, Bremen, Germany
Manuscript received 9th November, 2015; revised manuscript accepted 21st June, 2016

Abstract The need for an update of the calcareous nannofossil biozonations proposed by Martini (1971) andBukry (1973,1975), more than 40 years ago, prompted us to develop two new biozonations published in 2012 and2014, one for the Miocene through Pleistocene interval and one for the Paleogene interval (Backman et al., 2012;
Agnini et al., 2014). These biozonations are here combined into a single Cenozoic biozonation from low and middle
latitudes. A key strategy has been to employ a set of selected biohorizons for defining biozone boundaries, rather
than aiming for obtaining the highest possible biostratigraphic resolution. This approach is aimed to find a balance
between accuracy, applicability, and ease of communication and viability in practical geologic work. Each biozone
boundary is defined with a single biohorizon. Subzones and auxiliary markers are avoided in order to maintainstability to the new biozonation. Combining the Paleogene and Neogene biozonations, a total of 38 Paleogene
biozones and 31 Neogene-Pleistocene biozones are proposed: 11 Calcareous Nannofossil (CN) Paleocene biozones(CNP1–CNP11), 21 Eocene biozones (CNE1–CNE21), 6 Oligocene biozones (CNO1–CNO6), 20 Miocene biozones(CNM1–CNM20), and 11 Plio-Pleistocene biozones (CNPL1-CNPL11). Each of these 69 biozones contains one orseveral secondary biohorizons that are useful for biozone characterization. Age estimates are provided for all biozone
boundary markers and the majority of the additional biohorizons. These estimates are derived from astronomicallytuned cyclostratigraphies in the Pleistocene to middle Eocene (base of Chron C19n at 41.510Ma) interval andmagnetostratigraphy in the early Paleogene, back to the Cretaceous-Paleogene boundary.

Keywords calcareous nannofossils, biozonation, Cenozoic
1. Introduction
Nicholas J. Shackleton (1937–2006) was a leading marine
stable isotope and cyclostratigrapher during the late 20th
century. He also understood and embraced marine biostratigraphy: “Despite advances in magnetostratigraphy,
stable isotope stratigraphy and various manifestationsof cyclostratigraphy, it is still true that biostratigraphy isthe essential tool by which the geological evidence forenvironmental change is put into a temporal framework”(Shackleton et al., 1995).
The two major contributors to Cenozoic calcareous deep-sea sediments are calcareous nannofossils andplanktonic foraminifera. The study of these groups grew
and accelerated after the 2nd World War, concomitantlywith increasing geological studies related to hydrocarbon

exploration on the one hand and with the beginning ofsystematic sampling of short deep-sea sediment cores on
the other. Early efforts, devoted to research drilling ofdeep sea sediments, include the development of the piston
corer, first employed by the Swedish Deep Sea Expeditionof 1947–48, and thereafter during the numerous researchcruises with the R/V Vema under the leadership of Maurice Ewing.
In 1954, Milton N. Bramlette and William R. Riedel
published a seminal paper on the biostratigraphic valueof calcareous nannofossils. About 15 years later, this research field had grown to the extent that calcareous nannofossil biozonations began to emerge for different segmentsof the Cenozoic (Hay et al., 1967; Gartner, 1969; Bukry& Bramlette, 1970). The field continued to develop when122

Raffi et al.

scientific deep-sea drilling began in 1968, resulting in thefirst calcareous nannofossil biozonation based solely on
deep-sea drilling sediments and encompassing the entire
Cenozoic Era (Bukry, 1973). These early calcareous nannofossil biozonations were developed within two decades
after calcareous nannofossil biostratigraphy had been
established as a research field. Over four decades later,
Erlend Martini’s (1971) and David Bukry’s (1973, 1975)
biozonations are still used, although the need for revision
has grown in the light of new calcareous nannofossil biostratigraphic data that have accumulated over the past four
decades.
A large amount of calcareous nannofossil biostratigraphic data has become available during the past three
decades. These data represent primarily low- and middle-­
latitude environments from deep-sea sediments as well asfrom marine on-land sections in the Mediterranean andwestern Tethys region. Results have been put together
in two new calcareous nannofossil biozonations, one by
Backman et al. (2012) focusing on the Neogene and Pleistocene, and the other by Agnini et al. (2014) focusing on
the Paleogene. Below, these are referred to as BA12,14.
The underlying biostratigraphic information of both studies rely on the use of census data of individual calcareous nannofossil species in combination with short sample
distances, typically one or a few decimetres, as publishedin many separate articles. The biozonations by BA12,14
provided age estimates of species used for the definitionof biozone boundaries as well as for a plethora of otherbiohorizons within the biozones. These age estimates were
derived from direct calibration to magnetostratigraphic records or orbitally tuned cyclostratigraphies. A new code
system was employed for the biozones, explained in
BA12,14.
A common critical character of the two new biozonations is that neither of them aim to establish the highest
possible resolution in terms of number of biozones, butrather aim to employ a limited set of selected biohorizons
in order to establish a basic and stable biostratigraphic
framework for relative dating of marine sediments in low
and middle latitude settings using calcareous nannofossils. Other additional biohorizons are successfully usedin regional biostratigraphic schemes and often improvethe biostratigraphic resolution in specific time intervals,e.g., in the middle Miocene of the Mediterranean area, but
are not included as marker biohorizons for the reason explained above.
Here, these two biozonations are synthesised intoa single and coherent Cenozoic calcareous nannofossil­biozonation.
2. Biohorizons
Calcareous nannofossil biostratigraphy chiefly relieson the evolutionary appearance or extinction of individual species, forming recognizable changes in assemblage compositions. Such appearances or extinctions arecommonly referred to as “biohorizons”, “bioevents” andeven “datums”. The term biohorizons is here adopted forsuch events. As appears from BA12,14, the use of census data have in many cases revealed that the “absolutely”
first or last specimen (Base, Top) observed may not represent the optimal choice for the most precise placing of abiohorizon in chronostratigraphy. The first or last continuous presence of a species may be a better choice, for which
BA12,14 adopted the concepts “Base common” or “Topcommon”. It is considered that “Top” and Base” represent
concepts that are not easily confused with each other, as
is the case with other acronyms that have been used torepresent evolutionary extinctions or first appearances, forexample LO, which may stand for either Last Occurrenceor Lowest Occurrence.
Thus, in all but three cases, four different types of
biohorizons were employed by BA12,14: Top (T), Top
common (Tc), Base (B) and Base common (Bc). The three
exceptions refer to established species that virtually disappear from the biostratigraphic record during a definedinterval within their range: (1) Top absence (Ta) Gephyrocapsa spp. ≥4µm re-appearance in the early Pleistocene
after having been virtually absent for an interval following
its evolutionary appearance in the earliest Pleistocene; (2)Base absence (Ba) for the virtual disappearance of Reticulofenestra pseudoumbilicus for an interval during the late
Miocene following its evolutionary appearance during the
middle Miocene; (3) the cross-over (X) in abundance between two helicoliths in the early Miocene, namely fromdominant Helicosphaera euphratis to dominant Helicosphaera carteri. It remains uncertain whether or not these
two species represent an ancestor-descendant relationship.
3. Study areas, time scales andbiohorizon age estimate uncertainties
The relative order of the biohorizons that are used for
definition of biozone boundaries are well established fromnumerous deep-sea drilling sites and marine on-land sections. Age estimates of these biohorizons, however, arederived from a limited number of such sites in the Atlantic
and Pacific oceans, and from two marine on-land sectionsin the western Tethys.
The Cenozoic time scale is still under development,
showing less problems in the Neogene and more in the
Paleogene. When considering that this work represents a
synthesis of BA12,14 and the present problems of the Paleogene time scale, we have chosen to keep the time scale
combination employed by BA12,14 (Lourens et al., 2004;
Pälike et al., 2006; Cande & Kent, 1995), rather than converting age estimates of biohorizons to the Geomagnetic
Polarity Time Scale (GPTS) published in 2012 (Gradstein
et al., 2012).
In the Pliocene-Pleistocene interval, Backman et al.
(2012) provide ages for 24 biohorizons. 21 of these 24 age
estimates (88%) were derived from ODP Site 926 (lat. 4°N;
Ceara Rise, western tropical Atlantic), one from ODP Site

A Cenozoic calcareous nannofossil biozonation….: A synthesis

925 (lat. 4°N), one from the middle latitude North Atlantic ODP Site 607 (lat. 41°N), and one from ODP Site 653(lat. 40°N; Tyrrhenian Sea) (Figure 1). Among the age esti­mates of 39 Miocene biohorizons, 26 (67%) were derived
from ODP Site 926, three from ODP Site 925, five fromODP Sites 844 (lat. 8°N) and ODP 845 (lat. 9°N) in thetropical Pacific, and five from ODP Site 1218 (lat. 9°N) in
the tropical Pacific (Figure 1). The details about the calibration of all 63 Neogene and Pleistocene biohorizons arereported in Backman et al. (2012; chapter 3, tables 2, 4).
Only 5 of the 63 biohorizons are calibrated using magnetostratigraphy (ODP Sites 844, 845), the remaining thus
rely on astronomical tuning of lithostratigraphic data and,in two cases, oxygen isotope data. This reliance on cyclostratigraphy reflects the limited availability of sediment

180˚

240˚

300˚

123

sections from lower latitude settings having continuous
high-quality magnetostratigraphies. The ideal calibration
targets for calcareous nannofossil biohorizons would be insediment sections having both magnetostratigraphies andastronomically tuned cyclostratigraphies, so as to be able
to capture the details of the variations in sedimentation
rates between successive geomagnetic reversal boundaries.
It follows that the age estimates of individual biohorizons
may very well change when these are calibrated in sections
having both magneto- and cyclostratigraphies. Improved
age estimates of individual biohorizons will also permit
better assessments of the degree of diachrony/synchrony
between different regions if the biostratigraphic calibration occurs in more than one sediment section having bothmagneto- and cyclostratigraphy. Even if the presented age

0˚

60˚

120˚

180˚

90˚

90˚

60˚

1051
1052

30˚

1218 845

653

30˚

925

844

0˚

60˚

Cicogna
Possagno

607

0˚

926
522*

-30˚

-30˚

1262

-60˚

-60˚

-90˚

-90˚
180˚

240˚

300˚

0˚

60˚

120˚

Site 1218

180˚

Cande and Kent (1995)

Site 522*
Site 1052
Site 1051
Possagno
Cicogna
Site 1262

Pälike et al. (2006)

(Ma)

25

40

45

Danian
early

55

60

C29r

C28r

C29n

C27r

C28n

C27n

C26r

C25r

C24r

50

C26n

PALEOCENE

C25n

C23r

Thanetian Selandian
early

C24n

C22r

C21r

C22n

C21n

C20r

C19r

C20n

C18r

C19n

C17r

35

C23n

Ypresian
early

Lutetian
middle

EOCENE

C18n

C16r

Bartonian

C17n

C15n

C13r

30

C16n

C12r

C13n

C11r

C12n

C11n

C9r

C10r

C10n

OLIGOCENE

C8r

MIOCENE

Priabonian
late

Rupelian
early

C9n

C7An
C7Ar

C67r

C8n

C7n

GPTS
Age

Chattian
late

C6Cr

Epoch

C6Cn

Stage

65

Site 844

Site
653

Site 845

Site
607

Site 925
Site 926
Site 1218

(Ma)

0

10

15

C6Cr

C6Cn

C6Ar

C6Bn
C6Br

C6An

C6r

C6n

C5Er

C5Dn

C5Dr

C5En

C5Cr

C6AAr

Aquitanian Chatt.
late
OLIG.

Burdigalian
early

C5Cn

C5Bn

C5Br

C5AD nr

C5AC nr

CAr

CAn

Serravall. Langhian
middleMIOCENE
C5r

C5n

C4Ar

C4n

C3Br

C3Ar

C3An

C3n

C2Ar

C2An

C2r

C2n

C3r

5

C4r

early

PLIOCENE

C4An

Tortonianlate

C5AA nr
C5AB nr

Agelate middle

PLEIST.

C1r

GPTS

Calab. Gel. Piac. Zanclean Messinianmid + early
late

C1n

Stage
Epoch

20

Figure 1: Geographic location and stratigraphic range of the Figurereference1sections considered in Backman et al. (2012) and Agnini et al. (2014)

Raffi et al.

124estimates may change as better calibrations become available, we consider that the present age estimates will likely
not differ by more than a few percent (1–2?), as the relative
order of the series of Neogene and Pleistocene calcareous
nannofossil biohorizons is well established.
In the Paleogene, Agnini et al. (2014) provided age
estimates for 54 biohorizons, 10 in the Oligocene, 31 in
the Eocene, and 13 in the Paleocene. All Paleogene biohorizons are calibrated against magnetostratigraphy infive deep-sea drilling sites from the Atlantic (four sites)

5.0
6.0

C2An
C2Ar
C3n

mid +
late
early

C3r
C3An

8.0
9.0
10.0

C3Ar
C3Br

C4n
C4r

late

7.0

Messinian Zanclean Piac. Gel. Calab.

4.0

C2r

C4An

C4Ar
C5n

Tortonian

3.0

C2n

middle late

2.0

C1r

PLIOCENE

1.0

C1n

early

0.0

PLEIST.

Age (Ma) GPTS Epoch Stage

14.0

C5AC nr

15.0

C5Bn

19.0
20.0
21.0

C5Cn
C5Cr
C5Dn

C5Dr
C5En
C5Er

C6n

CNPL9
CNPL8
CNPL7

CNPL6
CNPL5

C6r
C6Ar

23.0

C6Cn
C6Cr

late

C6Bn
C6Br

OLIG.

22.0

Gephyrocapsa (≥ 4µm)
/ P. lacunosa CRZ
Small Gephyrocapsa PRZ

Gephyrocapsa (≥ 4µm) BZ
C. macintyrei PRZ

D. brouweri TZ
D. pentaradiatus TZ

CNPL4

D. tamalis TZ

CNPL3

D.asymm. / R. pseudoum. CRZ

CNPL2

S. neoabies PRZ

CNPL1
CNM20

C. acutus TRZ
T. rugosus PRZ

CNM19

D.quinqueramus TZ

CNM18

N.amplificus TRZ

CNM17

Amaurolithus spp. BZ

CNM16

D. berggrenii BZ

CNM15

D. bellus BZ*

CNM14 R. pseudoumbilicus PRZ
CNM13

D. hamatus TRZ
C. coalitus BZ

CNM11

D. exilis PRZ

CNM10

D. kugleri TRZ

CNM9D.variabilis PRZ

CNM8

C. premacintyrei TZ

CNM7

D. signus/
S. heteromorphus
CRZ

B Emiliania huxleyi (0.29)
T Pseudoemiliania lacunosa (0.43)
Ta Gephyrocapsa (< 4 µm)(1.06)
T Gephyrocapsa (>5.5 µm) (1.25)
B Gephyrocapsa (≥ 4 µm) (1.71)
T Discoaster brouweri (1.93)
T Discoaster pentaradiatus (2.39)
T Discoaster tamalis (2.76)
T Reticulofenestra pseudoumbilicus (3.82)
Bc Discoaster asymmetricus (4.04)
T Ceratolithus acutus (5.04)
B Ceratolithus acutus (5.36)
T Discoaster quinqueramus (5.53)
T Nicklithus amplificus (5.98)

B Nicklithus amplificus (6.82)
B Amaurolithus spp. (7.39)
B Discoaster berggrenii (8.20)
Ba R.pseudoumbilicus (8.80)
T Discoaster hamatus (9.65)
B Discoaster hamatus (10.49)
B Catinaster coalitus (10.79)
Tc Discoaster kugleri (11.60)
Bc Discoaster kugleri (11.88)

Tc Calcidiscus premacintyrei (12.57)

B Discoaster signus (15.73)
CNM6

S. heteromorphus BZ

CNM5

S. belemnos BZ

CNM4

H. carteri
PRZ*

CNM3

H. euphratis PRZ*

CNM2

S. disbel./T. carin. CRZ

CNO6

T. carinatus PRZ

Bc Sphenolithus heteromorphus (17.75)

C6An
C6AAr

24.0

Burdigalian

18.0

CNPL10BIOHORIZONST Sphenolithus heteromorphus (13.53)

Chatt. Aquitanian

17.0

C5Br

early

16.0

C5AD nr

middleC5AA nr
C5AB nr

MIOCENE

CAr

Serravall.

CAn

Langhian

C5r

13.0

Backman et al. 2012
CNPL11
C. cristatus PRZ

CNM12

11.0
12.0

CALCAREOUS NANNOFOSSIL
ZONESand Pacific (one site) and two marine on-land sections(Figure 2) from the western Tethys. The present latitudesof these sections are: 30°N for ODP Site 1051; 30°N for
ODP Site 1052; 26°S for ODP Site 522; 27°S for ODP Site
1262; 9°N for ODP Site 1218; 46°N for the Cicogna section; and 46°N for the Possagno section. The calibrationof the Paleogene biohorizons relies on linear interpolation
between successive geomagnetic reversal boundaries. It
follows that potential variations in sedimentation rates
within individual polarity zones are not accounted for

B Sphenolithus belemnos (19.01)

X Helicosphaera euphratis / H. carteri (20.89)

CNM1

S. conicus PRZ

Tc Triquetrorhabdulus carinatus (22.10)
B Sphenolithus disbelemnos (22.41)
T Sphenolithus delphix (23.06)

Figure 2: Proposed calcareous nannofossil biozones and biohorizons plotted versus the chronostratigraphic scale and the Geomagnetic Polarity Time
Figure 2a
Scale (GPTS; Lourens et al., 2004). Biohorizons: blue characters indicate biohorizons calibrated in deep-sea sections, brown characters indicate
biohorizons calibrated in land sections. TRZ = Total Range Zone; CRZ = Concurrent Range Zone; BZ = Base Zone; TZ= Top Zone; PRZ = Partial
Range Zone; B = Base; Bc = Base common; T = Top; Tc = Top common. Figure 2a: Miocene to Pleistocene biostratigraphy. OLIG. - Oligocene;
PLEIST. = Pleistocene; Chatt. = Chattian; Serravall. = Serravallian; Piac. = Piacenzian; Gel. = Gelasian; Calab. = CalabrianA Cenozoic calcareous nannofossil biozonation….: A synthesis

when calculating age estimates of the calcareous nannofossil biohorizons.
The Paleogene time scale remains problematic, particularly in the middle Eocene through Paleocene interval.
Agnini et al. (2014) therefore combined two different timescales for the Paleogene. The orbitally tuned time scale of
Pälike et al. (2006) is used from the top of Chron C6Cn.3n(23.278Ma) to the base of Chron C19n (41.510Ma). This
time scale provided revised age estimates for all geomagnetic reversal boundaries between the above two chronboundaries. From top Chron C20n to base Chron C29n,
the time scale of Cande & Kent (1995) is used, leading toan age estimate of the Cretaceous/Paleogene boundary of
65.0Ma. Renne et al. (2013) convincingly demonstrated
that this boundary occurred at 66.0Ma. Yet, the present uncertainties in the middle Eocene-Paleocene interval madeit reasonable to adopt the Cande & Kent (1995) time scale.
For most Paleogene biohorizons, however, Agnini et al.
CALCAREOUS NANNOFOSSIL
ZONES

C6Cn

27.0
28.0
29.0

C8n
C8r
C9n
C9r
C10n
C10r
C11n

30.0
31.0
32.0

late

C7An
C7Ar

Chattian

C67r

C11r

E. formosa CRZ

late

C15n

C18n

40.0
41.0

C18r
C19n

42.0

C19r

H. compacta TZ
D.
saipanensis TZ
CNE20
CNE21

C13r

C17r

T Sphenolithus delphix (23.06)
T Sphenolithus ciperoensis (24.36)

B Sphenolithus distentus (30.0)

CNO1

C17n

Tc Triquetrorhabdolus carinatus (22.10)
B Sphenolithus disbelemnos (22.41)

S. distentus/
S.predistentus
CRZ

C13n

C16n

BIOHORIZONS

S. ciperoensis
TZ

R. umbilicus TZ

middle

39.0

CNO5

CNO2

EOCENE

38.0

T. carinatus
PRZ

C12r

C16r
37.0

CNO6

D. bisectus
PRZ

Priabonian

36.0

S. conicus PRZ

CNO3

C12n

Bartonian

35.0

CNM1

CNO4

33.0
34.0

CNM2

S. disbelemnos/
T. carinatus CRZ(2014) provided information about their distance fromnearest higher geomagnetic chron boundary. For example,
the Base of Prinsius martinii occurred 11% from the topof Chron C28n at ODP Site 1262 (see Table 1 in Agnini
et al., 2014), where the entire duration of Chron C28n
equals 100%. When new age estimates will be available
for the boundaries of Chron C28n, the Base of Prinsius
martinii is easily recalculated considering that this biohorizon falls 11% from the top of this polarity zone. This
reasoning is applied to all other biohorizons.
With respect to present uncertainties regarding age estimates of middle Eocene through Paleocene biohorizons,the errors presumably will be larger close to the Cretaceous/Paleogene boundary and decrease when approaching Pälike’s et al. (2006) time scale in the middle Eocene.
For example, the oldest biohorizon used in the new biozonation is Base Coccolithus pelagicus, having an age estimate of 64.76Ma on the Cande & Kent (1995) time scale.

T Sphenolithus predistentus (26.93)

Rupelian

26.0

C7n

OLIGOCENE

25.0

C6Cr

early

24.0

early

23.0

Aquitan.

22.0

C6AAr
C6Bn
C6Br

MIOCENEAge (Ma) GPTS Epoch Stage Agnini et al., 2014; Backman et al. 2012

CNE19

C. isabellae /C. reticulatum CRZ

CNE18

I. recurvus PRZ

CNE17
CNE16

C. erbae TRZ
C. grandis PRZ

CNE15

D. bisectus /S. obtusus
CRZ

CNE14

C. reticulatum
BZ

125

T Reticulofenestra umbilicus (32.02)
T Ericsonia formosa (32.92)
Bc Clausicoccus subdistichus (33.88)
T Discoaster saipanensis (34.44)
Tc Cribrocentrum reticulatum (35.26)
B Cribrocentrum isabellae (36.13)
Tc Cribrocentrum erbae (37.46)
Bc Cribrocentrum erbae (37.88)
T Sphenolithus obtusus (38.47)

B Dictyococcites bisectus (40.36)

B Cribrocentrum reticulatum (42.37)

Figure 2b Aquitan. = AquitanianFigure 2b: Middle upper Eocene to Oligocene biostratigraphy.

Raffi et al.

126

43.0

C19n

C20n

44.0
45.0

C20r

46.0

49.0
50.0
51.0
52.0
53.0

C21r
C22n

C23n
C23r
C24n

54.0

C26r

60.0
61.0

C27n

62.0

C27r

63.0

C28n

64.0
65.0

Thanetian

C26n

Selandian

59.0

C25r

Danian

58.0

C25n

late

57.0

C. reticulatum
BZ

CNE13

R. umbilicus BZ
Nannotetrina spp.
PRZ

CNE12
CNE11

C. gigas TRZ

CNE9

N. alata gr. BZ

CNE8

N. cristata BZ

CNE7
CNE6

D. barbadiensis PRZ

C29r

D. sublodoensis /D. lodoensis CRZ

R. dictyoda
PRZ

CNE4

D. lodoensis /T. orthostylus
CRZ

CNE3

T. orthostylus BZ

CNE2

T. eminens PRZ
F. tympaniformis TZ

CNP11

D. multiradiatus /F. richardii gr. CRZ

CNP10

D. backmanii BZ

CNP9

D. mohleri BZ

CNP8

H. cantabriae BZ

CNP7

F. ulii BZ

CNP6 S. moriformis gr. BZ
CNP5

T. pertusus BZ

CNP4

P. martinii BZ

CNP3

P. dimorphosus
BZ

CNP2

C. pelagicus BZ

C28r
C29n

S. cuniculus/C.gigas
CRZ

CNE10

CNE1

PALEOCENE

56.0

C24r

early

55.0

CNE14

CNE5

C22r

Ypresian

48.0

C21n

early

47.0

CNE15

D. bisectus /S. obtusus
CRZ

C19r

middle42.0

C18r

Lutetian

41.0

C18n

EOCENE

40.0

Bartonian

CALCAREOUS NANNOFOSSIL
ZONESAge (Ma) GPTS Epoch Stage
Agnini et al., 2014

CNP1

B. bigelowi PRZBIOHORIZONSB Dictyococcites bisectus (40.36)

Bc Cribrocentrum reticulatum (42.37)
Bc Reticulofenestra umbilicus (43.06)
T Chiasmolithus gigas (43.96)
Bc Sphenolithus cuniculus (44.64)
B Chiasmolithus gigas (46.11)
B Nannotetrina alata gr. (46.80)
B Nannotetrina cristata (47.99)
T Discoaster lodoensis (48.37)
Bc Discoaster sublodoensis ‘5-rays’(48.96)
T Tribrachiatus orthostylus (50.66)

Bc Discoaster lodoensis (52.64)
B Tribrachiatus orthostylus (53.67)
T Fasciculithus tympaniformis (54.71)
T Fasciculithus richardii gr. (55.0)
B Discoaster multiradiatus (56.01)
B Discoaster backmanii (56.95)
B Discoaster mohleri (57.57)
B Heliolithus cantabriae (58.27)

B Fasciculithus ulii (60.31)
B Sphenolithus moriformis group (60.74)
B Toweius pertusus (circular) (62.03)
B Prinsius martinii (62.62)
Bc Praeprinsius dimorphosus (64.32)
Bc Coccolithus pelagicus (64.76)
T Cretaceous nannoflora = K/Pg

Figure 2c: Paleocene to middle Eocene biostratigraphy
Figure 2c

In the future, when the problems of the Paleogene time scale
are solved, this biohorizon will probably receive an age justyounger than 66Ma rather than just younger than 65Ma,­implying an age correction on the order of 1.0%. Again, therelative order of the series of Paleogene calcareous nannofossil biohorizons is well established, and changes in the order of
biohorizons are not expected, and, like in the Neogene case,
it is assumed that future corrections of age estimates of the
Paleogene calcareous nannofossil biohorizons will be limited
to <2% in low and middle latitude environmental settings.

4. A synthesis of the Cenozoic
calcareous nannofossil biozonations
A synthesis of the BA12,14 biozonations is presented
in Figures 2a (0-24Ma), 2b (21.5–42Ma) and 2c (39.5–
65Ma), showing 69 biozones together with chronostratigraphic information, biozone codes and primarybiohorizons. Primary biohorizons define biozone boundaries, with secondary biohorizons occurring within biozones. Information on these additional biohorizons andzonal assemblage descriptions is available in BA12,14.

A Cenozoic calcareous nannofossil biozonation….: A synthesis

127

Figure 3: Duration of the CN zones throughout the Cenozoic. MIOC. = Miocene; OLIG. = Oligocene; PLIOC. = Pliocene; PLEIS. = Pleistocene

1.
2.
3.
4.
5.

Five logical types of biozones were defined. These include:
Taxon Range Zone (TRZ)
Concurrent Range Zone (CRZ)
Base Zone (BZ)
Top Zone (TZ)
Partial Range Zone (PRZ)

in the upper part of the middle Eocene, in the Oligocene),
and intervals showing increased rates of taxonomic evolution which resulted in shorter durations of the biozones.

5. Cenozoic calcareous nannofossil
biostratigraphy and biochronology:
adjustments, changes, novelties
Each biozone has a code consisting of a combined acro- As explained by BA12,14, these efforts were meant to intenym for Calcareous Nannofossil (CN) and for each series grate the classical biohorizons that have proved to be reliable(P = Paleocene, E = Eocene, O = Oligocene, M = Mio- in Bukry’s (1973) and Martini’s (1971) biozonations with newcene, PL = Pliocene-Pleistocene), and a number for each biohorizons that could substitute the problematic biohorizons
biozone, starting from the base (= biozone 1) of the series. in Bukry’s and Martini’s work. This synthesis therefore partly
The Paleogene is subdivided into 11 Paleocene (CNP1– relies on older biozonations and employs several biozone defiCN11), 21 Eocene (CNE1–CNE21) and 6 Oligocene nitions that refer to biohorizons used also by Martini (1971)(CNO1–CNO6) biozones. The Neogene is subdivided and Okada and Bukry (1980), hereafter referred as M71 andinto 20 Miocene (CNM1–CNM20) and 11 Pliocene-­ OB80, respectively. A direct comparison among BA12,14,
Pleistocene (CNPL1-CNPL11) biozones.
M71 and OB80 is shown in Figure 4a–c, differences and muThe proposed biozonations provide variable biostra- tual features are shown in Figure 5a–e and summarized in the
tigraphic resolution for each series. Average biostrati­ following subchapters, and are discussed in stratigraphic order.
graphic resolution is: 0.9Myr/biozone in the Paleocene,
1.0Myr/biozone in the Eocene, 1.8Myr/biozone in the 5.1 Paleocene: Figures 4a, 5c
Oligocene, 0.9Myr/biozone in the Miocene, and 0.5Myr/ During the Danian Stage, species belonging to Coccobiozone in the Pliocene-Pleistocene.
lithus, Praeprinsius and Prinsius evolved, which often
In Figure 3, the biozones are plotted together with their became dominant components of the early Paleocene asduration in millions of years (Myr). The figure roughly semblages and providing distinct biohorizons. These taxa
synthesises the imprint of the evolutionary history of Ce- are used in place of species belonging to the genera Crunozoic calcareous nannofossils, marking both intervals ciplacolithus and/or Chiasmolithus that were included inwith long durations of the biozones (in the lower Eocene, the M71 and OB80 biozonations. In this way, taxonomicRaffi et al.

128

problems related to small sized species of Cruciplacolithus and Chiasmolithus disappear. Other novelties introduced in the Paleocene biozonation include three new
biohorizons, Base Sphenolithus moriformis, Base Discoaster backmanii and Top Fasciculithus richardii group.
These biohorizons are approximate substitutes for problematic biostratigraphic markers such as the evolutionary
ZONES

CNE13

49.0
50.0
51.0
52.0
53.0

C23r
C24n

59.0

CP9a

NP13

NP12

CNE1

30.0

NP7

CP5

NP6

CP4

NP5

C28n
C28r
C29n
C29r

27.0

29.0

CP6

C26n

CNE4

CNE2

C25r

63.0

25.0

NP10

NP8
?

C27r

24.0

28.0

NP9

62.0

C6Cn

CNE3

CP7

C27n

CNE5

23.0

NP11

CP8a

C26r

CNE7
CNE6

22.0

C6AAr
C6Bn
C6Br

CNP11
CNP10
CNP9
CNP8
CNP7

32.0

NP4

CNP6
CNP5
CNP4

CP2

NP3

CP1b

NP2

CP1a

NP1

CNP3
CNP2
CNP1

Figure 4: CN biozones plottedversusFigure4a the biozonations of Martini (1971)
and Okada & Bukry (1980), and the Geomagnetic Polarity Time Scale(GPTS; Lourens et al., 2004). Dashed lines correspond to biohorizons thatlack of reliable calibration and, in some cases, unclear taxonomic definition.
Figure 4a: Paleocene to middle Eocene interval

36.0

Martini
1971

CN1b

NN1

38.0
39.0

CP19b
CP19a

C9n
C9r
C10n
C10r

CNO5
NP24

CNO4

CP18
NP23

C11r
C12n

C12r

CP17
CP16c
CP16b
CP16a

C13r
C15n

C16n

C17n
C17r

CP15b

CP15a
CP14b

CNO3
NP22
NP21

C18r

CNO2
CNO1
CNE21

NP20
?
NP19

CNE20
CNE19

NP18

CNE18

NP17

CNE17
CNE16

C18n

C19n
42.0

CNO6

C8r

40.0
41.0

CNM1

NP25

C7An
C7Ar

C8n

C16r
37.0

Agnini et al. 2014

CNM2

C67r

C13n
34.0

Okada and
Bukry 1980

CN1a

C7n

33.0

35.0

CP3

C6Cr

C11n

31.0

Epoch
early

NP14

C25n

61.0

65.0

CP8b

C24r

60.0

64.0

CP10
CP9b

late

58.0

CNE8

ZONES
Age (Ma) GPTS

26.0

C23n

PALEOCENE

57.0

CP12b

CP11

early

56.0

CNE9

C22n
C22r

CNE10

CP13a

CP12a

C21r

54.0
55.0

NP15

MIOCENE

48.0

C21n

early

47.0

EOCENE

46.0

CNE11
CP13b

C20r

late

44.0

CNE12

CP13c

OLIGOCENE

C20n

CNE14

early

43.0

NP16

5.2 Eocene: Figures 4a, 5b
The complex Eocene biostratigraphic framework presumablyreflects the variability of environmental/climatic conditions
during this long time interval, with relatively stable intervals
interrupted by several episodes of climatic instability that resulted in alternating phases between higher and lower rates

late

CP14a

C19n
C19r

Agnini et al., 2014

CNE15

C18r

42.0

45.0

Martini
1971

EOCENE

41.0

Okada and
Bukry 1980

C18n

middle

40.0

Epoch

middleAge (Ma) GPTS

appearances of Ellipsolithus macellus, Heliolithus riedeli,and Tribrachiatus bramlettei, which M71 and OB80 usedin the lower Paleocene, the upper Paleocene and the Paleocene/Eocene transition, respectively. Furthermore, othernew biohorizons are the Base of Fasciculithus/Lithoptychius ulii, the first species appearing in the second radiation of the fasciculiths, and Base Heliolithus cantabriae,
the first representative of the genus Heliolithus. Both biohorizons approximately replace Base F. tympaniformis andBase H. kleinpellii, the precise positioning of which can beblurred by the presence of transitional morphotypes.

CNE15
CP14a

NP16

CNE14

C19r

Figure 4b: Middle upper Eocene
to Oligocene
interval
Figure4b

A Cenozoic calcareous nannofossil biozonation….: A synthesis

ZONES

3.0
4.0
5.0
6.0

C3n

mid +
late

PLEIST.

C2n

C2Ar

NN21
NN20

CN13b

C3r
C3An

8.0
9.0
10.0

C3Ar

C4r
C4An

C4Ar
C5n

16.0
17.0
18.0
19.0
20.0
21.0

CN11b
CN11a
CN10c
CN10b
CN10a

NN16

C5Bn

middleC5AC nr
C5AD n
r

CNPL4
CNPL3

NN13

CNPL2

NN12

CNPL1
CNM20

CNM19

CN9b

NN11b

CN9a

NN11a

CN8b

NN10

CNM18

CNM16

NN9

CN6

NN8

CNM12

CN5b

NN7

CNM11

CN5a

NN6

CN4

NN5

CNM13

CNM10

CNM8

CNM7

C5Br
C5Cn

CN3

C5Cr

NN4

CNM6

C5Dn

C5Dr
C5En

CN2

C5Er

NN3

C6n

CN1c

C6Ar

C6Bn
C6Br

NN2

23.0

C6Cn
C6Cr

CNM3
CNM2

OLIG.

22.0

CNM5

CNM4

C6r

C6An

CN1b
CN1a

of some biohorizons, characterized by scattered abundance
patterns and/or taxonomic ambiguities, was forced by thelack of better alternatives. Examples include Base Discoaster
sublodoensis and Top Chiasmolithus gigas. Biohorizons that
rely on species belonging to Chiasmolithus are not used, thatis C. solitus, C. grandis and C. oamaruensis, because thesetaxa have problematic taxonomy or provide unreliable/uncertain biostratigraphic signal. Isthmolithus recurvus is not used
for similar reasons. These traditional biohorizons have been
replaced with species belonging to genus Cribrocentrum,
C. reticulatum and C. erbae, which, by contrast, provide
more robust biostratigraphic signals. Some Eocene intervals
still suffer from a deficiency of good biohorizons, and future
improvements will possibly be developed by means of highresolution studies of critical intervals.

CNM15

CNM14

CN7

C6AAr

24.0

CNPL6
CNPL5

CNM9

CAr
C5AA nr
C5AB nr

CNPL9
CNPL8
CNPL7

NN15+NN14CAn

MIOCENE

15.0

CN12a

CNPL10

early

14.0

NN17

CN8a

C5r

13.0

NN18

CN12c
CN12b

Backman et al.
2012
CNPL11

CNM17

11.0
12.0

CN12d

C3Br

C4n

late

7.0

NN19

CN13a

C2r
C2An

CN15
CN14b
CN14a

middle late

2.0

C1r

PLIOCENE

1.0

C1n

early

0.0

Martini
1971

early

Age (Ma) GPTS Epoch

Okada and
Bukry 1980

129

NN1

CNM1

NP25

CNO6

Figure 4c: Miocene to Pleistocene interval. OLIG. = Oligocene

Figure 4cof taxonomic evolution. Therefore, the Eocene nannofossil
biostratigraphy includes intervals of more closely spaced biohorizons as well as intervals with few available biohorizons.
Examples are the highly resolved biostratigraphy in the lower
part of the Ypresian Stage (lower Eocene) and in the transitioninterval Bartonian – Priabonian (middle-late Eocene), withintervening intervals having only a limited number of usefulbiohorizons. As shown in Figure 5b, 18 classical biohorizons
have been replaced in the Eocene zonation. The replaced
taxa have, for example, displayed sporadic and discontinuous abundance patterns, represented lower quality and/or
limited datasets, and/or have been affected by ambiguous
taxonomy. There are exceptions to this plan because the use

5.3 Oligocene: Figures 4b, 5c
The Oligocene is characterized by low biostratigraphic resolution, caused by a low rate of taxonomic evolution andhence a lack of useful biohorizons in low and middle latitude
marine settings. The Oligocene biozones presented by Agnini
et al. (2014) approximately parallel Bukry’s (1973) biozonation (Figure 4b). Major differences with previous biozonations are in the lower Chattian and at the Oligocene-Miocenetransition. Top Sphenolithus predistentus is considered to be
the most distitinctive biohorizon among three closely spacedbiohorizons occurring within 0.35Myr: Base S. ciperoensis,
Top S. predistentus and Top S. distentus. In the uppermost
Oligocene, Top acme Cyclicargolithus abisectus and Top
Dictyococcites bisectus have limited correlation value andare replaced with Top Sphenolithus delphix .
5.4 Miocene - Pleistocene interval:
Figures 4c, 5d–e
In the lowermost Miocene, at the Pliocene/Pleistocene transition and within the Pleistocene intervals, the biozonationsof BA12,14 provide only a slight improvement in biostratigraphic resolution compared with the M71 and OB80 biozonations, whereas the reliability of some biohorizons, usedas biozone boundary markers, significantly improved.
Helicosphaera recta and Discoaster druggii show
problematic distributions, representing examples of lesssuitable M71, OB80 biohorizons for Miocene biozone
boundary definitions. These are replaced by other biohorizons, including those related to the distribution patterns of
Sphenolithus delphix and S. disbelemnos.
In the lower Pliocene interval, biohorizons presently
considered to be of limited quality were not employed: thedisappearance of Amaurolithus primus and A. tricorniculatus are not used for definition of a biozone boundary
because the two taxa are characterized by low and discontinuous occurrences, and remain poorly calibrated. In the upper Pliocene Top Discoaster surculus is not used. The shortinterval between the successive extinctions of D. surculus
and D. pentaradiatus are not included in the biostratigraphic
scheme because of problematic distribution patterns.

Raffi et al.

130

a



OLIGOCENE
GO OUT

1. Ta C. abisectus
2. T D. bisectus
3. T S. distentus
4. B S. ciperoensis
5. Tc C. subdistichusb

1. T S. ciperoensis
2. B S. distentus
3. T R. umbilicus
4. T E. formosa

 STAY INc

PALEOCENE

1. GO OUT
2.
1. B C. eodela
2. B3.
D. nobilis
3. B4.
H. riedeli
4. B H. kleinpellii
5.
5. B F. tympaniformis
6. B E. macellus
7. B C. danicus
8. B C. tenuis

1.COME IN
2.reticulatum
1. T C.
2. B C.
3.isabellae

1. Bc C. subdistichus
2. T D. saipanesis
3. Bc R. umbilicus
4. T C. gigas
5. B C. gigas
6. B N. alata gr.
7. B D. sublodoensis
8. T T. orthosylus
9. B D. lodoensis

 STAY IN
1. B D. multiradiatus
2. B D. mohleri

COME IN

1. T S. delphix
2. T S. predistentus
3. Bc C. subdistichus

EOCENE1.
GO OUT
2.
1. Ta C. abisectus
3.
2. T D. barbadiensis
3. B4.
I. recurvus
4. T C. oamaruensis
5.
5. T C. grandis

6. T C. solitus
7.-8. B & T D. bifax
9. T B. gladius
10. B N. fulgens
11.-12. B & T B. inflatus
13. B C. crassus
14.-15. B & T T. contortus
16. B D. diastypus
17. B T. bramlettei
18. B Rhomboaster spp.



 STAY IN

3. Tc C. erbae
4. Bc C. erbae
5. T S. obtusus
6. B D. bisectus
7. B C. reticulatum
8. Bc S. cuniculus
9. B N. cristata
10. T D. lodoensis
11. B T. orthostylus
12. T F. tympaniformis
13. T F. richardii gr.



COME IN1.
1. T F. richardii gr. 2.
2. B D. backmanii 3.

3. B H. cantabriae
4. B F. ulii
5. Bc S. moriformis gr.
6. Bc T. pertusus (circular)
7. B P. martini
8. B P. dimorphosus spp.
B C. pelagicus

Figure 5: Changes, exclusions and novelties among calcareous nannofossil biostratigraphic markers; bars = 5μm. Photomicrographs from different
sources: Agnini et al., 2007, 2014; Fornaciari et al., 2010; Norris et al., 2012; Raffi et al., 2006. Figure 5a: Photomicrographs of Oligocene taxa.
Figure 5b: Photomicrographs of Eocene taxa. Figure 5c: Photomicrographsof Paleocene taxa; H. riedeli after Okada & Thierstein, 1979; C. danicus
Figure 5a-c
after Varol, 1998

A Cenozoic calcareous nannofossil biozonation….: A synthesisd

PLIOCENE - PLEISTOCENEGO OUT

1. A E. huxleyi
2. T D. surculus
3. T A. primus, A.tricorniculatus
4. B C. rugosuse STAY IN
1. B E. huxleyi
2. T P. lacunosa
3. T D. brouweri
4. T D. pentaradiatus
5. T D. tamalis
6. T R. pseudoumbilicus
7. Bc D. asymmetricus
8. T C. acutus
9. BC. acutus

MIOCENEGO OUT

1. B D. loeblichii
2. B D. neoerectus
3. T H. ampliaperta
4. T S. belemnos
5. T T. carinatus
6. B D. druggii
7. T H. recta

 STAY IN

1. T D.quinqueramus
2. B Amaurolithus spp.
3. B D. berggrenii
4. T D. hamatus
5. B D. hamatus
6. B C. coalitus
7. B D. kugleri*
8. T S. heteromorphus
9. Bc S. heteremorphus

131

COME IN

1. Ta Gephyrocapsae ≥ 4µm
2. T Gephyrocapsae > 5µm
3. B Gephyrocapsae ≥ 4µm

COME IN

1. T N. amplificus
2. B N. amplificus
3. Tc D. kugleri
4. Bc D. kugleri
5. Tc C. premacintyrei
6. B D. signus
7. X H. euphratisH.carteri
8. Tc T. carinatus
9. B S. disbelemnos
10. T S. delphix

Figure 5: Continued. Figure 5d: Photomicrographs of Pliocene-Pleistocene taxa. Figure 5e: Photomicrographs of Miocene taxa

In the Pleistocene, the rapid evolution among the ge- resulting in an increase in some intervals, as in the middle
Figure 5d-e
nus Gephyrocapsa provides a series of useful biohorizons and upper Eocene, or no improvement in others, as in most ofthat made it possible improve the biostratigraphic schemes the Oligocene, when compared to the previous biozonations.
of M71 and OB80. Morphometric concepts are used for Several additional biohorizons are included within each biodiscriminating species within the genus Gephyrocapsa, zone. However, the introduction of subzones is avoided withwhich has proved to be reliable for stratigraphic correla- the aim to obtain a more stable Cenozoic biozonation that istion over wide geographic distances and that provide a applicable in practical geologic work. In spite of the fact that­robust biochronology.
some stratigraphic intervals still lack reliable biohorizons,e.g., within parts of the Eocene, improvements may possibly
6. Conclusions
be obtained in the future by means of high resolution studies
The generation of an abundance of new calcareous nanno- of critical intervals.
fossil biostratigraphic data over the past three decades have
A total of 69 Cenozoic biozones are defined using a
resulted in two new Cenozoic biozonations (Backman et al., new code system, referring to the series and a number
2012; Agnini et al., 2014). Here, a combined Cenozoic syn- for each biozone. The 38 Paleogene biozones comprisethesis of these two biozonations is presented. The new data- 11 Calcareous Nannofossil (CN) Paleocene biozones
sets consist of biostratigraphic information acquired at higher (CNP1–CNP11), 21 Eocene biozones (CNE1–CNE21),
resolution and through semi-quantitative counting methodol- and 6 Oligocene biozones (CNO1–CNO6); the 31
ogies using sediments from both DSDP/ODP/IODP deep-sea Neogene-­
Pleistocene biozones comprise 20 Miocene
sites and on-land marine sections. The number of useful bio- biozones (CNM1–CNM20) and 11 Plio-Pleistocene
horizons variably influences the biostratigraphic resolution, biozones (CNPL1–­CNPL11).

132

Raffi et al.

Age estimates are assigned to all biozone boundary
biohorizons as well as to most additional biohorizons.
These estimates are derived from astronomically tuned
cyclostratigraphies in the Pleistocene through middle
Eocene interval, and from magnetostratigraphy fromthe middle Eocene back to the Cretaceous-Paleogene
boundary.
Acknowledgements
Samples and data of this research were partly provided
by the Ocean Drilling Program (ODP) and the Integrated
Ocean Drilling Program (IODP) sponsored by the U.S.
National Science Foundation (NSF) and participating
countries under management of Joint Oceanographic Institutions (JOI). We thank Richard Denne and an anonymous reviewer for constructive comments that improved
the manuscript. Support from Università degli Studi”G. d’Annunzio” (IR), Università degli Studi di Padova(CA), and Stockholm University and the Swedish Research Council (JB) is acknowledged.
References

Agnini, C., Fornaciari, E., Raffi, I., Rio, D., Röhl, U. & Westerhold,T. 2007. High-resolution nannofossil biochronology of middle
Paleocene to early Eocene at ODP Site 1262: implications forcalcareous nannoplankton evolution. Marine Micropaleontology, 64: 215–248. doi:10.1016/j.marmicro.2007.05.003.
Agnini, C., Fornaciari, E., Raffi, I., Catanzariti, R., Pälike, H.,
Backman, J. & Rio, D. 2014. Biozonation and biochronology
of Paleogene calcareous nannofossils from low and middle
latitudes. Newsletters on Stratigraphy, 47: 131–181. doi:
10.1127/0078-0421/2014/0042.
Backman, J., Raffi, I., Rio, D., Fornaciari, E. & Pälike, H. 2012.
Biozonation and biochronology of Miocene through Pleistocene calcareous nannofossils from low and middle latitudes.
Newsletters on Stratigraphy, 45: 221–244. doi: 10.1127/00780421/2012/0022.
Bramlette, M.N. & Riedel, W.R. 1954. Stratigraphic value of discoasters and some other microfossils related to recent coccolithophores. Journal of Paleontology, 28: 385–403.
Bukry, D. 1973. Low–latitude coccolith biostratigraphic zonation. Initial Reports of the DSDP, 15: 685−703. doi: 10.2973/
dsdp.proc.15.116.1973.
Bukry, D. 1975. Coccolith and silicoflagellate stratigraphy, northwestern Pacific Ocean, Deep Sea Drilling Project Leg 32.
Initial Reports of the DSDP, 32: 677–701. doi: 10.2973/dsdp.
proc.32.124.1975.
Bukry, D. & Bramlette, M.N. 1970. Coccolith age determinations
Leg 3, Deep Sea Drilling Project. Initial Reports of the DSDP,
3: 589−611. doi: 10.2973/dsdp.proc.3.118.1970.
Cande, S.C. & Kent, D.V. 1995. Revised calibration of the geomagnetic polarity time scale for the Late Cretaceous andCenozoic. Journal of Geophysical Research, 100 (B4):6093–6096. doi: 10.1029/94JB03098.

Expedition 342 Scientists, 2012. Paleogene Newfoundland sediment drifts. IODP Prel. Rept., 342: 1–263. doi:10.2204/iodp.
pr.342.2012.
Fornaciari, E., Agnini, C., Catanzariti, R., Rio, D., Bolla, E.M.,
Valvasoni, E. 2010. Mid-latitude calcareous nannofossil biostreatigraphy, biochronology and evolution across the middle
to late Eocene transition. Stratigraphy, 7: 229–264.
Gartner, S. 1969. Correlation of Neogene planktonic foraminiferand calcareous nannofossil zones. Transactions of the Gulf
Coast Association of Geological Societies, 19: 585–599.
Gradstein, F.M., Ogg, J.G., Schmitz, M.D. & Ogg, G.M. 2012.
The Geologic Time Scale 2012. Elsevier, Amsterdam, 1–2:
1–1144.
Hay, W.W., Mohler, H., Roth, P.H., Schmidt, R.R. & Boudreaux,J.E. 1967. Calcareous nannoplankton zonation of the Cenozoic of the Gulf Coast and Caribbean–Antillean area, andtransoceanic correlation. Transactions of the Gulf Coast
Association of Geological Societies, 17: 428–480.
Lourens, L.J., Hilgen, F.J., Shackleton, N.J., Laskar, J. & Wilson,
D. 2004. The Neogene Period. In: F.M. Gradstein, J.G. Ogg& A.G. Smith (Eds). A Geological Time Scale 2004.
Cambridge University Press, Cambridge: 409–440.
Martini, E. 1971. Standard Tertiary and Quaternary calcareous
nannoplankton zonation. In: A. Farinacci (Ed.). Proceedingsof the Second International Conference on Planktonic Microfossils, 2: 739−785.
Okada, H. & Thierstein, H.R., 1979. Calcareous Nannoplankton
Leg 43, Deep Sea Drilling Project. In: B.E Tucholke, P.R.
Vogt et al. (Eds). Initial Reports of the DSDP, 43: 507–573.
Okada, H. & Bukry, D. 1980. Supplementary modification andintroduction of code numbers to the low-latitude c­ occolith
biostratigraphic zonation (Bukry 1973, 1975). Marine­Micropaleontology, 5(3): 321–325.
Pälike, H., Norris, R.D., Herrle, J.O., Wilson, P.A., Coxall, H.K.,
Lear, C.H., Shackleton, N.J., Tripati, A.K. & Wade, B.S.
2006. The heartbeat of the Oligocene climate system. Science, 314: 1894–1898. doi: 10.1126/science.1133822
Raffi, I., Backman, J., Fornaciari, E., Pälike, H., Rio, D., L­ ourens,L., Hilgen, F. 2006. A review of calcareous nannofossil astrobiochronology encompassing the past 25 million years.
Quaternary Science Review, 25: 3113–3137.
Renne, P.R., Deini, A.L., Hilgen, F.J., Kuiper, K.F., Mark, D.F.,
Mitchell III, W.S., Morgan, L.E., Mundil, R. & Smit, J.
2013. Time scale of critical events around the Cretaceous-­
Paleogene boundary. Science, 339: 684–687. doi: 10.1126/
science.1233948.
Shackleton, N.J., Baldauf, J., Flores, J.A., Iwai, M., Moore, T.C.,
Raffi, I. & Vincent, E. 1995. Biostratigraphic summary for
Leg 138. Proceedings of the ODP, Scientific Results, 138:
517–536. doi: 10.2973/odp.proc.sr.138.127.1995.
Varol, O., 1998. Paleogene. In: P.R. Bown (Ed.). Calcareous
Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series, Chapman and Hall (Kluwer­Academic Publishers): 200–224.